Heat exchange apparatus and method of use

ABSTRACT

A heat exchanger comprises a plurality of first heat exchange tubes extending through the exchanger, and through a plurality of laterally extending heat exchanger chambers, each chamber having at least one entry from a first chamber and at least one exit to a second axially adjacent chamber, and each chamber having a plurality of transverse interconnecting zones, each of which is defined by at least two of said tubes, and at least one first zone has an entry to said first chamber and at least one second zone, different from said first zone, has an exit to said second chamber. Also included is a vessel for mixing or distributing streams of a first fluid passing axially from an upstream to a downstream location, which comprises transverse baffles across said vessel in at least two successive rows, which rows of baffles define an open transverse chamber, the baffles in successive rows having a different spatial distribution across the vessel. Preferably the apparatus has the heat exchanger with the distributor downstream of it, and the whole apparatus is a compact reformer.

This application is a continuation of Ser. No. 09/261,653 filed Mar. 3,1999 which claims benefit of Provisional No. 60/051,898 filed Jul. 8,1997.

The present invention relates to an apparatus for heat exchange betweenfluids and/or for mixing of fluids, those fluids being different and/orat different temperatures.

In many process operations there are heat exchangers involving transferof heat from a first to a second fluid. The exchange may be to coolexhaust gases from a combustion reaction and/or to preheat gases priorto reaction. The two fluids may move in countercurrent or cocurrentdirections and may move with one fluid in a core and the other in asurrounding shell, or one may move in a tube or tubes passing thorough achamber containing the other fluid. In EPA-450872 a compact reformer hasreaction tubes for an exothermic reaction inside a chamber packed withcatalyst for an endothermic reaction. The exiting endothermic reactionproducts in the chamber preheat the exothermic reactants passing in acore and surrounding annulus inside the chamber. In EPA-643618 andEPA-703823 the endothermic reaction occurs in the tubes and theexothermic reaction in the chamber, and the exothermic reactants arepreheated by passage in annuli surrounding the exit endothermic tubes.In EPA-703823 one preheated exothermic reactant, usually air, passesinto the reaction chamber through a perforated distribution plate, whichforms a wall of air which moves up the chamber until it meets thepreheated fuel outlets at which time autoignition occurs to produceflames which pass around and along the endothermic tubes to effectreaction therein. The exiting combustion gases from the exothermicreaction preheat the incoming endothermic reactant.

The above arrangements do not give as uniform preheating of theexothermic reactants as may be desired, nor as uniform a temperaturedistribution of the air entering the reaction chamber as may be desired.

The present invention concerns apparatus for and methods of obtaininggreater uniformity in the preheating and/or temperature distribution.

The present invention provides a heat exchanger, which comprises aplurality of first heat exchange tubes extending through the exchanger,and through a plurality of laterally extending heat exchanger chambers,each chamber having at least one entry from a first chamber and at leastone exit to a second axially adjacent chamber, and each chamber having aplurality of transverse interconnecting zones, each of which is definedby at least two of said tubes, and at least one first zone has an entryto said first chamber and at least one second zone, different from saidfirst zone, has an exit to said second chamber.

The present invention provides a heat exchanger, which comprises aplurality of first heat exchange tubes extending through the exchangerand through a plurality of laterally extending heat exchanger chamberscomprising a first chamber and a second and third chamber axiallyadjacent thereto and on either side thereof, each chamber beingseparated from each adjacent chamber by a partition, in which are aplurality of discrete openings, and each chamber having a plurality oftransverse interconnecting zones, each of which is defined by at leastthree of said tubes, a first partition and a second partition opposingsaid first partition, and with said openings in different zones and apassage through said zones between at least one first opening in a firstpartition and at least one second opening in said first partition, andat least a third and a fourth opening in said second partition.

The present invention also provides a process for effecting heatexchange between a first fluid passing through a vessel and a secondfluid in a plurality of first tubes extending through said vessel andthrough a plurality of laterally extending heat exchange chambers, eachchamber having a plurality of transverse interconnecting zones, whichcomprises passing at least one stream of said first fluid into a firstchamber, effecting contact of said fluid and more than one of said tubesand then passing a stream of said fluid subsequent to said contact fromsaid first chamber into a second chamber axially adjacent to said firstchamber, so that said fluid passes through said chambers in an axial andlateral direction.

The present invention also provides a process for effecting heatexchange in a vessel between a first fluid passing through a pluralityof laterally extending heat exchange chambers in said vessel in mutualaxial relation in said vessel and a second fluid passing in a pluralityof first tubes, which extend through said vessel and through saidchambers, each chamber having a plurality of transverse interconnectingzones, which comprises passing at least two streams of said first fluidinto different zones in a first chamber, effecting contact of each ofsaid first streams and more than one of said tubes to give second andthird streams, mixing said second and third stream in a different zoneto produce a mixed stream and passing said mixed stream from saiddifferent zone into a second chamber axially adjacent to said firstchamber, so that said fluid passes through said chambers in an axial andlateral direction.

The heat exchanger is a hollow vessel containing the plurality ofchambers and the heat exchange tubes. The vessel may be of curved, e.g.circular, or ellipsoidal, or rectilinear e.g. square or rectangularcross section, and may have a longitudinal axis substantially normal toits radial axis, as in a right cylinder. Preferably its height to widthratio is 10:1 to 2:1. The vessel may be of metal, e.g. steel, orinsulating material, e.g. brick or stone, construction and especially inthe case of a metal walled vessel, may have an insulating externallayer.

The first heat exchanger tubes are of heat conducting material such ascarbon fibre reinforced material or ceramics but preferably of metal,especially high temperature resistant steel. The tubes may be dispersedin the vessel in a random or regular array, in particular in at least 2such as 2-6 rows, in which the tubes in adjacent rows may be in line oroffset with respect to one another. The tubes may be parallel in one ortwo directions, so any tube is a member of two rows, the axis of one rowbeing normal to the axis of the adjacent row or at 45° to said latteraxis; the axis of one row may also be normal to the axis of the next rowbeyond the adjacent row. Thus the tubes may be in rectilinear rows, eachtube being a constant distance from each of its 4 nearest neighbouringtubes or having 8 nearest neighbours, 4 of these at one distance and thenext 4 at a longer distance. The tubes may also be in non rectilineararrays. There may be at least 2, e.g. at least 10, first heat exchangetubes such as 2-5000, preferably 10-576, first heat exchange tubes inthe vessel. They may be distributed in a square or rectangular patternin the vessel, preferably in a square pattern and with the number oftubes in each row the same or alternating by one. They may be in atriangular pitch or a rectilinear pitch, e.g. square pitch, the rows inthe rectilinear pitch being optionally parallel to or at 30-60°, e.g.45°, to the walls of a notional or actual sheath surrounding theoutermost of the tubes in the array in the vessel.

The first tubes may extend through the vessel reactor linearly,especially in a direction parallel to the longitudinal axis of thevessel, in particular for right cylindrical vessels. For rectangularvessels the tube axis is usually parallel to a longitudinal edge.Advantageously the tubes pass through opposed faces, e.g. top and bottomof the vessel. However the tubes may also pass at any angle through oneof said opposed faces, rather than substantially normal thereto, and maypass through a side face of the vessel. The tube may also pass in anon-rectilinear fashion, e.g. in a curved fashion, which may be in asingle plane, as in an arc of constant or varying radius, or in aserpentine fashion, e.g. a sinusoidal fashion, or the tube may be inmore than one plane, e.g. in a regular or irregular helix.

The exchanger usually has insulation either surrounding the externalwall of the vessel and/or in a layer on the inside of that wall.

The vessel is subdivided axially with a plurality of laterally extendingchambers, each chamber usually extending across the full internal widthof the vessel. There may be at least 2, such as at least 5, suchchambers especially 2-200 or 10-60. The first tubes pass through morethan one chamber, especially through each chamber. The chamberspreferably extend laterally normal to the longitudinal axis of at leastone tube passing through it, in particular all of said tubes, and/orextend laterally normal to the longitudinal axis of the vessel,especially both. The relative height (axial length) of the chamber tothe lateral width of zones in said chamber i.e. the gap between saidfirst tubes is usually up to 10:1, e.g. 0.1:1 to 10:1, such as up to5.0:1, e.g. 0.2-3.0:1, 0.2-0.8:1 or 1-2:1. Advantageously the individualchambers are substantially parallel to one another, so the first andsecond partitions which constitute floors and ceilings of each chamberare preferably substantially parallel.

Each chamber is subdivided into a number of transverse zones (e.g. atleast 10 zones such as 10-1000), the relation of which to each other andother chambers will be described with reference to the first chamber,and the second and third chambers adjacent to it on either side.

The first chamber has among its zones, at least two and preferably 6,such as 6-50 entry zones, in which each zone has an opening to entryfrom the second chamber and at least two, and preferably at least 6,such as 6-50, exit zones, in which each zone has an opening to exit intothe third chamber. The relation between the number of zones to thenumber of tubes may be up to 2:1, e.g. 0.5-2.2:1, while the ratiobetween the number of entry zones to the number of exit zones in any onechamber is usually 0.5-2:1, e.g. 0.1-1.2:1, preferably substantially1:1. The zones usually extend in both lateral directions throughout thechamber and substantially all the chamber has been divided into zones.The zones usually interconnect with each other in the chamber and themajority especially substantially all, usually interconnect with zonesin neighbouring chambers as described further below. Ignoring the spacebetween the outermost tubes and the walls of the vessel, each zone isdefined by the walls of at least 3 or 4 tubes passing through thechamber. The zone is defined by at least 3 tubes when these are arrangedin a triangular pattern and by at least 4 tubes when these are in asquare or rectangular pattern. Irregular patterns of tubes can requireat least 3-6 tubes to define a zone. Each zone has at least 1 andusually 2 tubes common to its neighbouring zone.

A first zone has an entry from the next (e.g. second) chamber and asecond zone has an exit to the other adjacent (e.g. third) chamber. Nozone has both such an entry and such an exit, so the first and secondzones are different. At least one first entry zone may be adjacent to atleast one second exit zone, or may be spaced from the second zone by atleast one, e.g. 1-4, but especially 1 third zone, which has neither suchentry nor such exit. Thus advantageously an entry zone may be spaced bya third zone from an exit zone, which is itself spaced by a furtherthird zone from a further entry zone; thus 6 zones in question arepreferably in a straight line across the width of the chamber.Alternatively an entry zone may be adjacent to an exit zone, itselfadjacent to a further entry zone, all the zones preferably in a straightline across the chamber. Preferably the entry and exit zones in each ofthe second, first and third zones are in the same plane, so the firstfluid moves up the vessel in that plane. When the exit zone issurrounded by 2 or more entry zones in one, e.g. the first chamber, thenthe overall effect is to mix the portions of the first fluid enteringthe first chamber via the entry zones and eject them through the exitinto the next, e.g. third chamber, whereupon a portion passes to oneexit zone in that chamber and another portion passes to another exitzone in that chamber. In this way the fluid is divided, mixed andredivided and remixed with the same or different streams of fluid, ineach case with contact of 2 or more tubes in each zone. By this meansthe temperature of fluid in each chamber progressively becomes moreuniform as the fluid moves up the vessel from chamber to chamber.

In each chamber there are usually at least 4 zones in any lineardirection, and especially 0-3 zones, e.g. 0-1 zones, between each entryzone and each exit zone. In particular at least one entry zone is spacedfrom the vessel wall by at least one, e.g. 1-3, such as 1 tube, andespecially at least one, e.g. 1-3, such as 1 zone; the nearest exit zonefrom said entry zone is also preferably spaced from the vessel wall byat least one, e.g. 1-3, such as 1 tube or especially at least one, e.g.1-3, such as 1 zone. In addition each chamber preferably has at least 2entry zones spaced apart and at least 2 exit zones spaced apart, all ina straight line across the chamber in particular with 0 or 1 zonesbetween each entry and exit zone.

The first heat exchange tubes may be the only ones passing through thechambers, but preferably there is at least one second heat exchange tubepassing through the chambers. The diameters, cross section shapes andareas of the first and second (and any subsequent tubes) may be the sameor different; preferably the first tubes are larger and may be forcountercurrent heat transfer to the first fluid passing through thevessel while the second tubes may be smaller and for cocurrent heattransfer from the first fluid or countercurrent radiation heat transferfrom the first tubes. The second and further tubes may be symmetricallydisposed with respect to said first tube, e.g. equidistant to two ormore first tubes. The second and further tubes may be arranged regularlyas described above with the first tubes: in particular the first andsecond tubes are in rows which are parallel in two directions to oneanother. Thus, preferably there is a first regular array of said firstexchange tubes and a second regular array of second heat exchange tubesaxially extending through the exchanger and preferably of differentdiameter from said first exchange tubes. The second tubes are preferablyin alternate rows with the first tubes, in line therewith or especiallyoffset therefrom, i.e. with each tube of one kind at the centre of asquare (in plan view) with 4 nearest neighbours of another kind at thecorners of the square. The second tubes may alternate with first tubesin 2 directions normal to one another or only in one of thosedirections. The tube centre/tube centre spacing between the first tubesin any direction may be the same or different from that spacing betweenthe second tubes in that direction and that spacing between the firstand second tubes may be the same or different from either of the abovespacings. Preferably all these tube centre/tube centre spacings aresubstantially the same. The ratio of the number of first tubes to secondtubes may be 1:3 to 3:1, especially 10-14 to 14-10, or substantially1:1. The first tubes may be arranged with a triangular pitch with thesecond tubes in each alternate triangle, or may be in a rectilinear,especially square pitch.

The presence of first and second heat exchange tubes passing through theheat exchanger chambers is a particularly important aspect of theinvention especially in the method of the invention in which a firstfluid passes through the chambers, and a second fluid passes through thefirst tubes, while a third fluid passes through the second tubes, thedirection of flow of the second fluid is counter current to that of thethird fluid, and to the overall axial flow of the first fluid.

At least one of the first and second heat exchange tubes, preferably thefirst tubes and optionally both, is provided with means for enlargingthe effective external surface area thereof. The enlargement means maybe integral with the tube, or non integral therewith but in directthermal contact with the tube; both kinds of enlargement means may bepresent if desired. The enlargement means is usually one or more fins orribs on the tube, the fins or ribs being continuous or discontinuousthrough the chamber. They may be straight or curved e.g. spiral orhelical along the tube length in the chamber. The non integralenlargement means may be in the form of a heat conducting body havingone or more fin or rib, said body being extended round the tube in thechamber, with or without attachment to the tube. Conveniently the nonintegral means may have a fin or rib extending outwardly from, e.g.normal to, a base, which may have a flat surface for contacting thetube; thus this means may be a flexible elongate body of T-shaped crosssection tightly wound round the tube to provide good thermal contactbetween the tube and the base and hence provide heat to the fin or rib.

In the method of the invention, a second fluid, e.g. a gas or a liquidor mixture thereof, moves in the first tubes and heat is transferredbetween the tube walls and the first fluid (e.g. a gas or liquid ormixture thereof) passing through the zones in each chamber. A firststream of the first fluid may enter the first chamber, contact at least2 of the tubes in the zones and pass into the second chamber;alternatively, or in addition, a first and second stream of the firstfluid may separately enter the first chamber, each stream contacting atleast one tube and then the first and second streams may mix and pass tothe second chamber. Preferably each stream entering an entry zone in onechamber contacts at least 4, e.g. at least 8, heat exchange tubes beforeit leaves that chamber. Preferably the first fluid passes throughsuccessive chambers countercurrent to a second fluid passing through thefirst tubes, while especially a third fluid passes in the second tubescocurrent with the first fluid and countercurrent to the second fluid.Advantageously the first and second fluids are gases and the third is agas or a liquid, (especially when the second tube diameter is smallerthan that of the first tube). In particular the second fluid is anendothermic reaction product, e.g. from steam reforming of a gaseoushydrocarbon, e.g. of 1-4 carbons such as methane, or a partial oxidationof such a hydrocarbon, while the first fluid is a gas comprisingmolecular oxygen such as air and the third fluid is a fuel, e.g.hydrogen or a gaseous hydrocarbon of 1-5 carbons such as methane,ethane, propane or butane or carbon monoxide. Advantageously heat istransferred from the second fluid via first tubes to the first fluids,and hence from first fluid to third fluid (via second tubes) especiallyto preheat the air and fuel before entering a combustion region of thevessel, the combustion heating up the endothermic reaction. If desiredthe first tubes may contain heat transfer solids, e.g. inert solids suchas ceramic material and/or solid catalyst for the endothermic reaction.At least some of the heat transfer between the first tube and the secondtube in the chambers is usually by radiation, e.g. at least 5% or 20%,such as 5-10%, 10-50%, or 20-40%, such as about 30%, the rest beingprimarily by convection.

Preferably in the process the first fluid passes through at least 1 andespecially at least 2 successive chambers in one plane, e.g. 5-30chambers, and then through at least 1 especially at least 2 successivechambers in a different plane, particularly at 45-135° to the firstplane, e.g. substantially normal to it, e.g. a further 1-30 chambers;thereafter the plane of movement may be changed again, e.g. as before atleast once more, such as 1-5 times further. If desired the plane ofmovement may be changed at a more frequent rate with increasing distancefrom the entry of first fluid.

The percentage of the entry and exit openings in any chamber to thetotal area of that chamber (i.e. including tubes) is usually 5-25%, e.g.10-20%, while the percentage of the entry and exit openings in anychamber to the total area of that chamber excluding the tubes (i.e. thetotal area of the zones) is usually 25-50.

In the apparatus of the invention the individual chambers may havecomplete partitions, also called barriers herein, between them apartfrom the entry and exit openings mentioned above, so they havesubstantially complete floors and ceilings. The barriers may beotherwise impermeable to first fluid forcing all that fluid to pass fromentry to exit zones before passing to the next chamber. However, ifdesired at least a portion, especially substantially all, of at leastone barrier between successive chambers, especially substantially allsuch barriers, are foraminous, with the percentage of the area of theholes to the total area of the barrier of 10-70%, especially 30-60%.Such perforated barriers allow some passage of the first fluid from eachchamber to the next other than via the entry and exit zones to reducethe back pressure and render the flow distribution even compared to useof solid barriers. Preferably however, the barriers are incomplete butnot foraminous.

The entry and exit openings may be in the form of slots in sheets orplates, or spaces between separate baffles. The barriers may be of aregular or irregular shape with straight or curved sides, so that theentries and exits may be of circular, ellipsoid, rectangular, square orother cross section. One barrier may completely cover the roof of one ormore zones; in particular there may be one or a series of barriersacross the width of the vessel. Thus there may be a series of rows ofbarriers of similar shape, e.g. with parallel longitudinal or laterallyextending sides; those may thus be the baffles mentioned above. Thesecond tubes may pass through at least two and especially substantiallyall of these barriers with parallel lateral extending sides butpreferably pass through only a proportion of said barriers especially atregular intervals, in particular through alternate barriers. When aseries of successive chambers has parallel sided baffles, the sides ofthe baffles may be coplanar through at least 2 successive chambers, e.g.substantially all, or the sides may be parallel to those of the bafflesin the next chamber but the sides may overlap (when viewed in planview). There is thus effectively no axial line of sight betweensuccessive chambers, thereby forcing the first fluid to move laterallyas well as axially between successive chambers especially in aserpentine manner. While baffles in one chamber may have sides parallelto the corresponding baffles in the adjacent chamber and/or axiallycolinear with those in the subsequent chamber, so that there may be 5-30of such chambers, it is preferable periodically to have a series ofbaffles for first successive chambers with such parallel sides and thena series of baffles for the next successive chambers with mutuallyparallel sides, but at an angle, e.g. 45-135° such as substantiallynormal to those in the first series. This change for the next successivechambers may be repeated one or more times, each group of chambershaving 1-50, e.g. 5-30, chambers. In this way portions of the firstfluid move through the vessel in one plane, prior to moving through thevessel in a different plane usually normal to the first. Thus there maybe an exchanger which comprises in successive chambers a first series ofbarriers with sides parallel in one direction and then a second seriesof barriers with sides parallel in a different direction; the first andsecond series of barriers may alternate. When there are first and secondtubes there are preferably baffles between alternate rows of first tubesin said first chamber and baffles between different alternate rows offirst tubes in said second chamber, said second tubes passing throughsaid baffles.

The first chamber may have a first partition which is a floor (or roofto the second chamber) with 2 transverse parallel sided slots, and asecond partition which is a roof (or floor to the third chamber) with 3transverse parallel sided slots, the sides being axially coplanar withthose in the first chamber, while for the floor of the second chamberthere are 3 such slots etc; after this series of such chambers the nextplane of the sides changes for the next series again with an alternating2, 3, 2, 3 number of slots. Generically the numbers of slots mayalternate by one between each successive chamber. The slots may thus goNorth/South for a series, then East/West, then North/South again. Withthe above arrangements of slots, the effect is preferably that the heatexchanger vessel when viewed in plan view has a regular pattern of tubeswith baffles through which first tubes pass and with an arrangement ofsecond tubes, slots and baffles through which the second tubes pass orare tangential thereto, the overall effect being that there iseffectively no line of sight through the heat exchanger, so that thefirst fluid can only pass with axial and lateral motion, rather thanaxial alone.

Advantageously the heat exchange tubes are inside a reactor with 2walls, preferably concentric walls. While both may be load bearing,advantageously the outer one is more load bearing than the inner one.The inner wall acts like a shroud or envelope surrounding all of thetubes to provide an annulus between the two walls, e.g. outer wall andshroud. The inner wall, e.g. shroud, is usually of heat conductingmaterial, e.g. metal or carbon fibre reinforced material, and may be incontact with one or more heat exchange tubes, but preferably is spacedfrom each tube. The inner wall may be of the same axial cross sectionshape as the outer reactor wall, e.g. concentric circles, but preferablythe axial sections shapes are different, e.g. the outer wall is circularand the inner one is ellipsoidal or rectangular, such as square. Theshroud may also hold in place in the reactor the barriers or partitionspresent between the chambers, and hence may help to locate the tubes.

This annulus in the reactor between shroud and reactor wall can containheat insulation, e.g. ceramic material, but preferably provides apreheating zone for first fluid prior to entry into the heat exchangerchambers at their upstream end; this zone also reduces the heat lossfrom the reactor by capturing the heat from the shroud and reusing it.The reactor wall may be provided at one or more locations, at least oneof which is distant from upstream heat exchanger chambers and near tothe downstream heat exchangers, with at least one orifice for entry ofthe first fluid, e.g. air, and especially fluid under compression, saidorifice(s) being in the reactor wall of the annulus. There may be morethan 1 orifice, especially 2-6, in particular spaced symmetrically aboutthe longitudinal axis of the reactor, usually in a plane normal to thataxis. The shroud or envelope at its end near to the upstream heatexchange chambers may have at least one entry location into that (orthose) heat exchange chamber(s) in particular 1-3 entries, e.g. one,into the one or more of the 3 most upstream heat exchange chambers,especially the most upstream chamber. Thus in use the air, e.g.compressed air, enters the reactor through the orifice(s) into theannulus, passes through the annulus, where via the shroud it is incocurrent heat exchange relationship with the first tubes and/orcountercurrent heat relationship to the first fluid moving through theheat exchanger chambers; the first fluid may be preheated to at least100° C. in this way before entry into the heat exchanger chamber fromthe annulus.

In one embodiment the process of the present invention also includespreheating the first fluid outside the heat exchanger chamber by heatexchange with first fluid inside said chambers, to give a preheatedfirst fluid prior to entry of the preheated first fluid into heatexchanger chambers; advantageously the preheating is in a directioncountercurrent to the direction of movement of first fluid in saidchambers. In particular the first fluid is passed through an annulusbetween the shroud and reactor wall, the shroud providing an envelopesurrounding the tubes.

The benefits of the heat exchanger and process of the invention mayinclude a better heat distribution across the width of the vessel to thefirst fluid when leaving the exchanger, e.g. at the top, and/or to thesecond fluid when leaving the exchanger, e.g. at the bottom, through thefirst tubes. In a further aspect the present invention also provides avessel for mixing or distributing streams of a first fluid passingaxially from an upstream to a downstream location, which comprisestransverse baffles across said vessel in at least two successive rows,which rows of baffles define an open transverse chamber, the baffles insuccessive rows having a different spatial distribution across thevessel. This arrangement of baffles may be present in a heat exchangerof the invention preferably after the first fluid has passed through theheat exchanger. Alternatively other heat exchanger systems may be usedin combination with the above arrangement of baffles. The baffles canact as spoilers to break up the flow of the first fluid and distributeor mix it.

The arrangement of baffles may be used as a mixing device for fluids,different in temperature and/or composition, e.g. for mixing at leasttwo different fluids, or one fluid in at least 2 streams at differenttemperatures. Preferably it is for mixing fluids at differenttemperatures, such as ones obtained from contact of one or more fluidswith heat exchange surfaces, in particular ones extending through thevessel as in the first tubes in the above mentioned publishedreferences. If one of the tubes is at a different temperature from therest, then first fluid passing it will be at a different temperaturefrom the rest leading to lack of uniformity at the top of the heatexchanger, which this aspect of the present invention seeks to remedywith the special arrangement of baffles to give a substantially uniformtemperature and composition fluid across the width of the vessel.

The arrangement of baffles is preferably used in a distribution devicefor fluids, e.g. ones having different axial velocities, in order toprovide a flow of fluid across a wide area, e.g. the vessel width, ofsubstantially constant velocity. The first fluid may first contact thebaffles in one or more than one stream, e.g. a stream emanating fromcontact of one or more fluids with heat exchange surfaces, in particularones extending through the vessel as in the first tubes of the previousapparatus of the present invention. Preferably the fluid is air and thebaffles provide a flow of air across the vessel of substantiallyconstant velocity, e.g. as a wall of air, in particular when the airmeets the fuel burners in the apparatus of the invention.

The vessel may as described above in respect of the heat exchanger interms of shape and construction, though need not have the first (andother tubes) in it. Thus in the upstream location in the vessel the 2streams of fluid may just have been passed into the vessel, or may beseparate from but on top of a heat exchanger with heat exchangesurfaces, that heat exchanger being inside the vessel or outside it butwith free movement of fluid from the exchanger into the vessel. In theformer case, with baffles and exchanger in the same vessel, the heatexchange surfaces may extend through the region of the vessel containingthe transverse baffles or may be absent therefrom, e.g. stop in thevessel below the baffles.

The baffles may be impermeable to the fluids, but preferably areforaminous, the total area of the holes in the baffles being 10-60%,e.g. 30-50%, of the total area of the baffles, and the size of theindividual holes being preferably on average less than one fifth of thesize of any heat exchange tubes passing through them, e.g. one twentiethto one fifth of the size. Advantageously the holes are all substantiallythe same size, especially in any particular row, though the holes insuccessive rows may be also of the same size or of progressivelyincreasing or especially progressively decreasing size.

The shapes of the individual baffles may be as described above for thebarriers in the heat exchanger.

The baffles are preferably in a vessel with at least some tubes passingthrough them, the spatial relationship between the vessel and the tubesbeing preferably as described above in relation to the heat exchangerand tubes. In particular the vessel may have first tubes passing throughit in one regular array, and second tubes passing through it in adifferent way; the description above provides further details on thespatial arrangement of the tube arrays. The first and second tubes maybe in rows parallel to one another or at 30-60°, e.g. 45° to oneanother. In particular, a pair of rows of first tubes is preferablyspaced by a row of second tubes and/or vice versa, especially when thefirst and second tubes are in parallel rows in two directions at rightangles. Preferably each first tube is surrounded by 4 second tubes andeach second tube is surrounded by 4 first tubes (apart from tubesadjacent to the vessel wall). The relation between the tubes and thebaffles is preferably as follows. The second tubes may pass between, butpreferably pass through, at least some of the baffles. The baffles mayhave laterally extending parallel sides, extending across substantiallythe internal width of the vessel and are located between at least someof the first tubes, e.g. 2-4. The sides of the baffles in a first roware usually at an angle, e.g. 45-135°, or substantially normal to thesides of the baffles in a second adjacent row. Preferably the number ofbaffles in one row is one more or less than the number in the adjacentrow. Advantageously with respect to a first row of baffles first andsecond tubes are in parallel rows interspaced between one another, androws of parallel sided baffles have alternate rows of second tubespassing through them, while with respect to a second row of bafflesadjacent to said first row of baffles, rows of parallel sided baffles insaid second row have each row of second tubes passing through them andeach row of first tubes passing between them, the direction of the sidesof said baffles in the second row being substantially at right angles tothe direction of the sides of the baffles in the first row; especiallywith respect to a third row of baffles adjacent to said second row ofbaffles, rows of parallel sided baffles in said third row have each rowof second tubes passing through them and each row of first tubes passingbetween them, the direction of the sides of said baffles in the thirdrow being substantially at right angles to the direction of the sides ofthe baffles in the second row, but substantially in the same directionas the sides in the first row. In particular the vessel has incombination the first, second and third row of baffles as described inthe previous sentence; especially the 3 successive rows of baffles areperforated and are each disposed with respect to the tubes and the wallsof the vessel such that in axial view the overall effect of the 3 rowsis to appear to occupy at least 80% of the cross sectional area of thevessel, excluding the tubes.

The method of distributing according to the invention comprises a methodof passing a first fluid axially through a vessel from an upstream todownstream location, wherein the fluid passes axially around successiverows of baffles laterally extending across the vessel, each successiverow being in a different spatial relationship across the vessel, so thatat least some of said fluid has lateral as well as axial movement. Whenmore than one stream of said first fluid is passed into the vessel, thestreams may be distributed separately in the method of the invention,but preferably the at least partly distributed streams, e.g. after thefirst row of baffles may be mixed, so the baffles overall effect amethod of mixing. In particular at least a portion of a first stream offluid passes axially between first tubes in a first row, and then passesaxially and laterally between first and second tubes in a second row,and optionally through at least one perforated baffle in said secondrow, and preferably at least a portion of said first stream passesaxially and laterally between first and second tubes in a third row andoptionally through at least one perforated baffle in said third row.

In preferred aspects of the invention the heat exchanger of theinvention has the distributor of the vessel of the invention downstream,e.g. on top of it. Extending in the vessel beyond the last baffle in adownstream direction are preferably the second tubes upon the end ofeach of which is mounted a fuel burner, e.g. a jet nozzle;advantageously the burner ends are in a transverse plane normal to thelongitudinal axis of the heat exchange/mixer/vessel. The distributorand/or mixer arrangement of baffles provides a uniform temperature andvelocity distribution of first fluid, e.g. air, which moves subsequentlyin the vessel up towards the burners while the air and fuel ignite(usually auto-ignite) producing elongate flames, which move around andalong the first tubes so that the first tubes, which for the endothermicreaction, are immersed in a sea of flame. The exiting combustion gasesfrom the burning in the vessel leave the vessel, optionally via anaccelerated movement through an annulus of upwardly converging diameter,the annulus surrounding the incoming first tubes; in this way theendothermic reactants are preheated and then heated by the combustion ofthe exothermic reactants. The combined heat exchanger, mixer/distributorcombustion vessel, (including burners), together with their associatedfirst and second tubes can form a compact reformer for reforminghydrocarbons to carbon monoxide and hydrocarbon with maximum internalheat distribution and minimum temperature for the exiting endothermicand exothermic reaction products. If desired the heat exchanger, mixerand tubes may be supported in the external apparatus via means to absorbelongations and stresses due to expansion e.g. bellows on the tubesheets used to support the tubes.

The present invention is illustrated in and with reference to theaccompanying drawings in which:

FIG. 1 is a cross section through the apparatus of the invention showingthe heat exchanger and a section 1A through the exchanger.

FIG.2 is a schematic drawing of the heat exchanger and distributor andsections though the exchanger in planes 2A, 2B, 2C, 2D and 2F.

FIG.3 is a cross section through the distributor and burners andsections through the mixer in planes 3A, 3B, 3C and 3D.

FIG.4 is a cross section through the combustion gas exit tubes of theapparatus.

Referring now to FIG. 1 a reactor 1 has elongate fuel tubes 2 extendingthrough it, proceeding in the direction 3 to fuel burners (not shown) atone end, and at the other ends at junctions 4 distributed along a fuelmanifold 5. Manifold 5 extends across the width of reactor 1 andprojects through outer walls 6 of the reactor 1 connecting with flexiblemetal hose 7, which in turn leads via inlet tube 8 to a fuel source orsources. Inlet tubes 8 are located in annular tubes 9 located inorifices 11 in the outer wall 6. The fuel tubes 2 are distributedbetween endothermic tubes 12 (see the cross section 1A) in an array ofalternating tubes; for clarity the endo tubes are only shown in thecross section. The array of tubes 2 is maintained in a square shroud 14which is spaced from reactor 1 by support rings 20 to form an annulus13; the rings 20 interact with support mountings 10 on the reactor wall6. Fuel manifold 5 is supported by shroud 14.

The reactor 1 is supported externally. Below the fuel manifold 5 is aflanged base 15 attached to a dished flanged end cover 16. A side airinlet 46 in the shroud 14 is located between the levels of the fuelmanifold 5 and support mounting 10; this side inlet 46 allows freemovement for air from the annulus 13 between shroud 14 and reactor wall6, in which at the downstream end of reactor 1 distant from cover 16 isan external air entry orifice 47. Endo gas product manifold 17 islocated internally of cover 16 and is spaced from an exit port hole 18by a bellows pipe 19.

In use, fuel, e.g. methane or hydrogen, passes into the reactor 1 viametal hose 7, fuel manifold 5, fuel tubes 2 and out into the reactionchamber, where the fuel is ignited usually autoignited. At the same timecompressed air enters reactor 1 via said external air entry orifice 47into the annulus 13 where it is preheated by to the fluids enclosedwithin the shroud 14 prior to entry through the side air inlet 46. Theair passes between tubes 2 and 12 to become further preheated and thenproceeds in the direction 3 to the fuel burners. For clarity detail ofthe features for the preheating are omitted (but see FIG.2).

FIG.2 shows the distribution of fuel and endo tubes 2 and 12respectively in the square shroud 14 through the heat exchanger 21,which is subdivided into 41 transverse chambers 22. FIG. 2 shows fiveregions of the heat exchanger, regions 23-27 corresponding to 9, 8, 8,8, 8 sets respectively of baffles 28 defining chambers 22. The numbers 2and 3 in the baffles 28 designate the numbers of slots 29 in each umbersof slots alternate through the length of the exchanger 21. Sections 2Ato 2E show the distribution of the first tubes 12 and fuel tubes 2 inthe various 2 and 3 slot baffle arrangements. Section 2A shows thesquare shroud 14 with support ring 20 enclosing the tubes 12 and 2,which are spaced by baffle 28 which has two slots 29 between tubes 12and through which pass fuel tubes 2; slots 29 are open. As shown Section2A has two slots in a North South direction; section 2B has three slots29 in the baffle 28, again in a N/S direction. Baffles 28 of thedisposition in section 2A and 2B are in regions 23, 25 and 27 of theexchanger. Section 2C has two slots 29 in a baffle 28, the slots beingin an East West direction, while section 2D has three slots 29 inbaffles 28, the slots being in an East West direction; Baffles 28 of thedisposition in sections 2C and 2D are in regions 24 and 26 of theexchanger. FIG.2 also shows schematically air distributors 30 above theexchanger 21.

FIG.3 shows the air distributors 30 in more detail with sections 3A, 3B,3C and 3D. Fuel tubes 2 lead to burners and to the ignition zone. Abovethe uppermost two slot baffle 28 are three levels of perforated platespoilers, a first spoiler 32 (of design shown in section 3A), a secondspoiler 33 (see section 3B) and a third spoiler 34 (see section 3C). Forclarity the endo tubes 12 are not shown in FIG.3 but only in sections3A-3D. Referring now to section 3A, this is a top plan view of spoiler32, showing fuel tubes 2 alternating with endo tubes 12 and offsetthereto. Between two pairs of rows of endo tubes 12 are two perforatedbaffles 35, through which fuel tubes 2 project. In use, the upcomingpreheated air emitted from the uppermost two slot baffle 28 passestowards the spoiler 32 where most air passes straight through the planeof the spoiler 32 but that under baffles 35 is diverted radially in aNorth South direction, apart from a small amount passing through theperforations. The upcoming air now reaches spoiler 33 as shown insection 3B, which is a top plan view. In spoiler 33 are five perforatedbaffles 36, between each row of endo tubes 12 and pierced by fuel tubes2. The baffles are in a North South direction. In use the air fromspoiler 32 passes through spoiler 33, except where baffles 36 restrictit and divert it, this time in a radial East West direction (apart fromthat moving through the perforations). Air then passes to spoiler 34(see section 3C) which has five perforated baffles 37 in an East Westdirection between each row of endo tubes 12 and pierced by fuel tubes 2;baffles 37 divert upcoming air in a radial NS direction (apart from thatmoving through the perforations). Section 3D is a top plan view of thethree spoilers 32-4 and their baffles 35-7 and shows that a verysubstantial part of the upcoming air passes through and/or is divertedby the baffles, the diversion movement being alternating betweenNS/EW/NS or EW/NS/EW.

FIG.4 shows combustion zone 38 interspaced by endo tubes 12, whichdownstream of the combustion zone 38 each pass through combustionannulus 39 of upwardly decreasing diameter surrounding endo tube 12 toaccelerate the exiting combustion gases past the endo tubes. Above theannulus 39 is the exit manifold 40 for the combustion gas, the manifoldbeing defined by upper and lower sheets 41 and 42 and side walls 43.Endo tubes 12 sealingly pass through upper sheet 41 into entry pipes 44fitted externally with secondary bellows 45 to absorb thermal movementsof the endo tubes.

The above detailed description is of one embodiment of the invention andis not meant to limit the scope of the invention in any way.

What is claimed is:
 1. A heat exchanger, which comprises a first regulararray of first heat exchange tubes extending through the exchanger andthrough a plurality of laterally extending heat exchanger chambers and asecond regular array of second heat exchange tubes axially extendingthrough the exchanger, two rows of said first heat exchange tubes beingspaced by a row of said second heat exchange tubes, said plurality ofheat exchanger chambers comprising a first chamber and a second andthird chamber axially laterally adjacent thereto and on either sidethereof, each chamber being separated from each adjacent chamber by apartition, in which are a plurality of discrete openings, and eachchamber having a plurality of transverse interconnecting zones, each ofwhich is defined by at least three of said first heat exchange tubes, afirst partition and a second partition opposing said first partition,wherein the first chamber has amongst its zones at least two entryzones, each entry zone having an opening to entry from the secondchamber, and at least two exit zones, each exit zone having an openingto exit to the third chamber, no zone having both an opening to entryand an opening to exit, and at least one entry zone is adjacent to atleast one exit zone or is spaced from the exit zone by 1 third zonehaving neither an opening to entry nor an opening to exit.
 2. Anexchanger according to claim 1 wherein each of the transverseinterconnecting zones is defined by at least four tubes.
 3. An exchangeraccording to claim 1 wherein an entry zone is spaced by a third zonefrom an exit zone which is itself spaced by a further third zone from afurther entry zone.
 4. An exchanger according to claim 1 wherein anentry zone is adjacent to an exit zone which is itself adjacent to afurther entry zone.
 5. An exchanger according to claim 1 wherein in eachchamber there are at least 4 zones extending in both lateral directionsthroughout the chamber and zero to one zones between each entry zone andeach exit zone.
 6. An exchanger according to claim 1 wherein said firstand second tubes are in rows which are parallel in two directions atright angles to one another.
 7. An exchanger according to claim 1wherein the second tubes are of different diameter from said firsttubes.
 8. An exchanger according to claim 1 wherein the first and secondpartitions are substantially parallel.
 9. An exchanger according toclaim 1 wherein the entry or exit openings in the partitions are in theform of slots in sheets or plates.
 10. An exchanger according to claim 9wherein at least some of the partitions are plates with transverse slotstherein.
 11. Apparatus comprising a heat exchanger for said first fluidas claimed in claim 1 and a vessel comprising a distributor fordistributing streams of said first fluid.
 12. Apparatus comprising aheat exchanger for said first fluid as claimed in claim 1 wherein saidfirst tubes are for hot endothermic reaction products in a heat exchangerelationship with second tubes for a third fluid which is an exothermicreactant, and with said first fluid which is a second exothermicreactant, the first and third fluids being for subsequent exothermicreaction to provide heat for said endothermic reaction.
 13. An exchangeraccording to claim 9 wherein the first and second partitions eachcomprise a series of parallel sided baffles wherein the series ofbaffles of said first and second partitions are parallel to one anotherbut wherein sides of said baffles overlap when viewed in plan view suchthat there is no axial line of sight between successive chambers.